Senate Republicans are strongly rejecting a White House plea for a delay in a new round of economic sanctions against Iran and are vowing to move forward with additional restrictions over the country’s nuclear weapons program.

Vice President Joe Biden, Secretary of State John Kerry, and top officials from the State and Treasury departments held a classified briefing on Wednesday afternoon for members of the Senate Banking Committee in an attempt to preempt congressional action on sanctions while Western leaders negotiate with Iranian officials. That panel would take the lead on any Senate consideration of such legislation.

Yet Republicans on the committee — and a number of Senate Democrats — remain unconvinced by the White House’s position following the briefing. After the classified meeting that included updates on diplomatic progress in Geneva last week, Sen. Chuck Schumer (D-N.Y.) was unmoved.

“I am dubious of the proportionality of the deal. While I am exploring further details, I am worried that we are reducing sanctions while Iran is not reducing its nuclear capabilities,” Schumer said.

The committee’s top Republican, Sen. Mike Crapo of Idaho, said he prefers more sanctions but will continue to listen to the administration before making a final decisions. Kirk was even more forceful.

“I do think we ought to accelerate sanctions,” said Kirk, a leading Israel supporter in the Senate. “The pitch was very unconvincing. It was fairly anti-Israeli.” Kirk told reporters that he’d met with Israeli officials earlier in the day who said a proposed deal with Iran would only set back their nuclear research effort by “24 days.”

He added: “This administration, like Neville Chamberlain, is yielding a large and bloody conflict in the Middle East involving Iranian nuclear weapons, which will now be part of our children’s future.”

A Treasury Department official said after the meeting that critics of the U.S. negotiating posture toward Iran “who claim our proposal is not a fair deal and makes too many concessions should ask themselves why the Iranians turned it down.” The official also didn’t rule out further sanctions — but said they shouldn’t come now.

“There may come a point where additional sanctions are necessary. At the same time, the Administration underscored the importance of Congress reserving its ability to legislate new sanctions for the moment when it would be most effective in order to give the current P5+1 negotiations the best chance to achieve our shared goals,” the official said, referring to the group of world powers engaged in diplomacy with Iran.

After leaving the meeting, Senate Democratic leadership and the Obama administration delegation’s lips were sealed. Senate Majority Leader Harry Reid (D-Nev.) and his entire leadership team as well as Biden and Kerry declined comment to a waiting pack of media.

Kirk also blasted Wendy Sherman, the State Department’s lead negotiator in the Geneva-based P5+1 talks with Iran, pointing out that she also led the Clinton administration effort in the 1990s to prevent North Korea from developing its own nuclear weapons. Despite U.S. efforts to supply that regime with food and nuclear reactors in a bid to end weapons research, North Korea exploded its own nuclear bomb in October 2006.

“I started questioning Wendy Sherman about her record on North Korea, and she surprisingly defended it to me,” Kirk said. “Her record to North Korea is a total failure and an embarrassment to her service.”

“It was an emotional appeal, and I have to tell you that I was very disappointed in the presentation. It lacked content,” complained Sen. Bob Corker (R-Tenn.), a Banking panel member who is also the top Republican on the Foreign Relations Committee. “I was stunned that in a classified setting, when you’re trying to talk with the very folks that would be originating legislation relative to sanctions, there would be such a lack of specificity.”

Senate Minority Leader Mitch McConnell (R-Ky.) told reporters he believes “we ought to be actually ratcheting up the sanctions against Iran. It’s pretty obvious that what the administration is promoting is something the Israelis think is a bad deal for them. It’s pretty clear the Sunni Arab allies of ours also think its a bad deal. Looking at it strictly from an American point of view, I think it’s a bad deal as well. So I’d be surprised if we do not have a debate on enhanced Iran sanctions.”

Before the meeting, Reid and other top Democrats were non-committal — although they have all expressed strong support for Israel. Israeli officials are quietly urging U.S. lawmakers to impose additional sanctions in order to force Iran to end its efforts to build a nuclear weapon.

“We should find out from them what went on” at the last round of Geneva negotiations, Reid said.

Reid added: “I hope we can work something out with Iran, but I am a person who really believes in the state of Israel. It’s a country that is surrounded by a number of countries that have been for decades now trying to get rid of them, wipe them off the face of the map….” he added.